Tuesday, May 27, 2008

Proof-of-Concept Backport Invokedynamic in Groovy

It is my first day of Google Summer of Code, and here is what I've done today ;-)

I have been reading hard and trying to understand Invokedynamic EDR since last week. It is quite difficult for me, who has little background of this kind of things. However, I have got some good sources for studying how invokedynamic work from John Rose's blog, Alex Tkachman's Method Handle code, Jeroen Frijters's blog, and RĂ©mi Forax's blog.

Although, there is no something complex like Jeroen's sample, here is a working version of Hello World that uses my backport of invokedynamic APIs.

package groovy.dyn.subject.vm5;

import groovy.dyn.CallSite;
import groovy.dyn.Linkage;
import groovy.dyn.MethodHandle;
import groovy.dyn.MethodHandles;
import groovy.dyn.MethodType;
import groovy.dyn.StaticContext;
import groovy.dyn.internal.CallSiteImpl;
import groovy.dyn.internal.StaticContextImpl;

import java.io.PrintStream;
import java.lang.reflect.Method;

public class InvokeDynamicSubject {

private static CallSite[] callsites;
private static final int NUM_OF_CALLSITES = 1;

static {
try {
Method method = InvokeDynamicSubject.class
CallSite.class, Object.class, Object[].class);
MethodHandle mh = MethodHandles.unreflect(method);
Linkage.registerBootstrapMethod(InvokeDynamicSubject.class, mh);
} catch (Throwable e) {
// do nothing now

private static void initCallSites() {
callsites = new CallSite[NUM_OF_CALLSITES];
callsites[0] = new CallSiteImpl(0,
new StaticContextImpl(
MethodType.make(void.class, String.class)

private static Object bootstrapInvokeDynamic(CallSite cs,
Object receiver, Object[] args) throws Throwable {
Method method=null;
CallSiteImpl csi = (CallSiteImpl)cs; // down cast: language specific
switch(csi.index()) {
case 0: {
StaticContext sc = cs.getStaticContext();
Class<?> c = sc.getCallingClass();
method = c.getDeclaredMethod(
MethodHandle mh = MethodHandles.unreflect(method);
return mh.invoke(receiver, args);
return null;

public void test() throws Throwable {
// System.out.println("Hello World");
MethodHandle mh = callsites[0].getTarget();
if(mh == null) {
bootstrapInvokeDynamic(callsites[0], System.out, new Object[]{"Hello World"});
} else {
mh.invoke(System.out, "Hello World");

No comments: